1. Field of the Invention
The present invention relates to a method for attaching a flat-shaped battery used in an apparatus that has a substrate and is to be attached to a rotary portion, and an apparatus to be attached to a rotary portion, having a substrate and a flat-shaped battery.
2. Description of Related Art
A flat-shaped battery called a coin battery or a button battery is used as a power source mainly for memory backup in information equipment, visual equipment, etc. The flat-shaped battery is a combination of a positive electrode can and a negative electrode can. The flat-shaped battery contains a power-generating element and is filled with a non-aqueous electrolyte solution. The power-generating element has a configuration in which a positive electrode material and a negative electrode material are placed via a separator.
On the other hand, the flat-shaped battery may be used as a power source of an apparatus to be attached to a rotary portion. As such an apparatus, there is an apparatus used for a tire air pressure monitoring system that monitors a tire air pressure of a traveling automobile. Some tire air pressure monitoring systems have a specification in which a transmitter containing a flat-shaped battery and also transmitting a detected pressure is attached to a wheel of a tire that is a rotary portion.
According to the above-mentioned specification, the flat-shaped battery rotates integrally with the tire to receive a centrifugal force, and the battery performance thereof may be degraded due to the flow of an electrolyte solution caused by the centrifugal force. Therefore, JP 11(1999)-242948 A proposes a method for attaching a battery in which a battery is mounted on an apparatus with a negative electrode material directed to a centrifugal force direction.
However, in the case where an apparatus containing a flat-shaped battery is attached to a wheel of a tire, it also is considered that the expansion of a battery can of the flat-shaped battery may adversely affect the apparatus. An example of such an apparatus includes the one in which a flat-shaped battery and a substrate are connected to each other via a terminal, and the flat-shaped battery and the substrate are buried in resin. In this apparatus, examples of the adverse effects caused by the expansion of the battery can include the following: the expansion of the battery can cause a force in a direction in which the terminal connecting the battery can and the substrate to each other is detached from the substrate; and further, the expansion of the battery can may deform the substrate via the resin between the battery can and the substrate. Therefore, when the expansion of the battery can is large, and the displacement amount of the terminal and the deformation amount of the substrate increase, this may lead to the detachment of the terminal from the substrate and the cracking of the substrate in worst cases.